Calibration in three dimensions: optimizing a two-parameter calibration technique to extend the range of an immunoturbidimetric urinary albumin assay into antigen excess.
I describe a general technique, called "two-parameter calibration," which allows precise determination of analyte from non-monotonic calibration plots and the calibration of immunoturbidimetric assays in antigen excess. Using three-dimensional calibration plots and relative-sensitivity curves, two optimal parameters may be selected from a number of possible options by using criteria presented here. Choosing two different values of delta At1-t2, the change in absorbance from time t1 to t2--as the reaction parameters in an immunoturbidimetric assay for albumin, I have optimized the choice of time interval for two-parameter calibration and extended the working range of the assay by three- to fourfold. The albumin assay shows excellent agreement of observed and expected values (r = 0.996) and also with results of a routine kinetic dye-binding method used on diluted plasma samples (r = 0.970).
Tillyer
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Department of Chemical Pathology, Royal Marsden Hospital, London, U.K.
D000418:Albumins / Q000032:analysis*; D000419:Albuminuria / Q000652:urine*; D001322:Autoanalysis; D002498:Centrifugation; D006801:Humans; D007118:Immunoassay; D009391:Nephelometry and Turbidimetry; D015203:Reproducibility of Results; D012709:Serum Albumin / Q000032:analysis / Q000276:immunology; D013223:Statistics as Topic
D000418:Albumins; D012709:Serum Albumin